Whether you're a beginner bird watcher or an experienced veteran, you're always within reach of a good pair of binoculars.  And a lot of birders will agree that they are always in search of the absolute best pair of binoculars in the world.  There are a lot of options out there, but what is the best for you?  Only you can decide that, but we may be able to help.  This guide is designed to help new birders understand how binoculars work, and give experienced bird watchers some insight on the more advanced aspects of their binoculars.

The Numbers

The first thing you'll notice about any pair of binoculars is the numbers in their name, such as 10x25, 8x32, 15x70, etc.  These numbers are used to describe the binocular's optical configuration, which is an indicator of what they can be used for.  

The first number is the power of the binocular, more commonly referred to as the magnification.  This number indicates how many times bigger the image seen through the binocular is when compared to the naked eye.  So, a 7x binocular will make objects in the distance appear about 7 times larger than they would if you were looking without binoculars.  

The second number is the size of the objective lenses of the binocular in millimeters (these are the lenses that are farthest away from your eye when looking through a pair of binoculars).  So, for example, a 10x50 binocular will magnify your view ten times, and has objective lenses that are 50mm wide.  

So what do the numbers actually mean?

Well, it can get complicated.  Since your eyes are different from everybody else's eyes, what you actually "see" through a pair of binoculars will vary slightly.  But, there are some basic rules that can be followed when we look strictly at those numbers.  Generally, a smaller magnification and larger objective size is more desirable.  But there are limitations to this, which is why every power/objective configuration has its advantages and disadvantages.  

Let's discuss power (magnification).  A higher magnification has an obvious advantage: it makes everything you look at appear to be closer, which is what a binocular is designed to do.  A lot of people assume that a higher magnification is obviously better because of this.  Unfortunately, the disadvantages to higher mangification make a binocular with high power useless in most birdwatching situations.  First, higher mangification usually means a narrow field of view, which can make tracking a moving bird difficult.  If you are unfamiliar with field of view, we'll talk more about that later.  Second, a high power 12x binocular not only makes birds appear 12 times closer, it amplifies accidental movement from your arms by 12 times as well.  It can be very difficult to track a bird when trying to overcorrect for unsteady arms.

Now let's discuss objective lens diameter.  Objective lenses can also be referred to as aperture, meaning the opening that light travels through to get through the rest of the binocular.  Either term is correct.  At face value, a larger objective lens usually means that it will collect more light, at the expense of size and weight.  Collecting light is important because it will allow you to make out more detail in situations where little light is available, such as cloudy days or early morning/late evening.  So, the goal is to get the largest objective size possible that is still comfortable.

Why are these factors important?  Birding is all about being able to easily track fast moving birds, while seeing as much detail as possible, and remaining comfortable while doing it.

Field of View

Field of view is a term used to describe the visible area at a given distance, commonly measured at 1000 yards and degrees.  When you see a binocular with a field of view of 300 feet at 1000 yards, that means that you can see a horizontal area about the size of an NFL football field at a distance of 1000 yards.  A wider field of view is usually more desirable, because it is another binocular quality that makes it easier to track a fast moving bird.  Magnification, objective lens size, and several other factors work together to determine what a binocular's field of view will be, and two nearly identical binoculars can have very different fields of view.

What magnification is best?

This question can really only be answered by you, because your preference will dictate which magnification you are most comfortable with.  However, it's safe to assume that 7x, 8x, and 9x magnifications are some of the most popular for serious bird watchers.  These are just enough power to see fine detail at a distance most birds will be encountered, while not being so powerful that they become difficult to use.  A magnification of 10x is also somewhat popular, but is on the higher end of what most birders would consider acceptable, because stability and field of view become limiting factors.  

However, most birders are known to have several pairs of binoculars with a wide range of mangification, so they are always prepared for any situation.  

Clarity and sharpness

You'll see these terms quite a bit when reading reviews about binoculars for birdwatching, along with a few others. All the quirks and qualities of a binocular work together (and sometimes against each other) to produce the image you see when looking through the eyepieces.  Here's a quick run down of what these terms mean.

• Clarity: This refers to the clarity of the internal glass components in a binocular.  Look through a pair of binoculars at an object in the distance.  Then remove the binoculars.  Does the image seem clear, or cloudy?  Higher quality glass will usually produce a clearer image, which is desirable.  
• Sharpness: This is slightly different than clarity.  An image can be clear, but fuzzy.  Sharpness refers to the resolution of the binocular, or how defined edges and details are when looking through the binocular.  
• Chromatic aberration: Referred to in shorthand as CA, this is the color fringing you see when looking at contrasting colored objects.  For example, the outline of a white bird against a clear blue sky.  A lot of chormatic aberration is easily seen by picking out the green or purple fringing along the edges of these objects.  Most binoculars will have some degree of chromatic aberration, but higher quality glass can correct it.  
• Color: Depending on lens coatings, glass type, and manufacturer, binoculars differ in how they transmit light, which means that the color you see through the binoculars may be slightly different than natural light.  It may appear warmer, cooler, or very true to real color.  
  
  

Waterproofing and fogproofing

All binoculars that are waterproof are fogproof, and vice-versa.  Waterproofing and fogproofing is accomplished during the manufacturing process by pumping all of the air out of the body of the binocular, and replacing it with an inert gas, thereby removing all moisture from inside the optical bodies.  Since there is no moisture, the inside of the lenses can never fog.  This is very important to bird watchers who pursue the hobby in all types of weather, because a pair of binoculars that fogs is useless.  Keep in mind that this only refers to the fogging on the inside of the lenses; there is no way to prevent fogging on the outside due to body heat and condensation.

Waterproofing and fogproofing isn't absolutely necessary.  Every birder should have an inexpensive pair of binoculars within reach, and they don't necessarily have to be fully waterproof.  The tradeoff is cost, because inexpensive binoculars will not usually be fogproof.  But, if you are going to spend over $100 on a pair of birdwatching binoculars, make sure the pair you choose is waterproof.  There is no reason a binocular at or above that price should not be able to stand up to adverse weather conditions. 

What binoculars do I need for birdwatching?

That really is the question, isn't it?  Below are several common binocular configurations that work best for bird watching.

• 7x50 Binoculars: A moderate 7x magnification is very easy for beginners to use, and a 50mm objective lens size collects ample amounts of light.  Good field of view on most models, which makes quick bird easy to track.  The only downside to a 7x50 design is that they are a little larger than some other configurations.  Most 7x50 binocular models are also very inexpensive, making the 7x50 binocular a perfect entry-level buy for the beginning birder.  
  
  Some good examples are the Celestron Cometron 7x50 binocular and Bresser Hunter 7x50 binocular.  Both are very affordable, and can come in handy as a spare even after you've upgraded to a higher class binocular.
   
• 8x32 Binoculars: A good compromise between power and medium size, 8x32 binoculars combine the most popular 8x magnification with a slightly smaller objective lens size.  The downside to 8x32 binoculars is that the 32mm objective will sacrifice some visibility and performance in low light compared to larger sizes, but it comes with the advantage of lighter weight, and as a result, more comfortable use.  
  
  Some good 8x32 binoculars for birdwatching are the Celestron Nature DX 8x32, Celestron Trailseeker 8x32, Vixen New Foresta 8x32, and Zen-Ray ZRS HD 8x32 binoculars.
   
• 8x42 Binoculars: The 8x42 binocular is probably the most popular configuration used by birders, because it combines the versatile power of 8x magnification with a larger objective lens for good overall performance in all conditions.  Again, 8x is the most popular because it makes birds appear 8x closer while not being so powerful that it becomes difficult to follow them.  The larger 42mm objective size is an industry standard that most birders utilize because it's the best compromise of weight and performance.  Most 8x42 birdwatching binoculars are much higher quality than the 7x50 and 8x32 models available, and can be found in prices ranging from $100 to, well... how deep are your pockets?  
  
  Some great 8x42 bird watching binoculars are the Bresser Everest 8x42, Celestron Granite 8x42, Celestron Nature DX 8x42, Celestron Trailseeker 8x42, and Zen-Ray ZRS HD 8x42.
  
  Some manufacturers have a slightly different apporach to the 8x42 binocular, and have increased the objective size to 43mm.  This doesn't make much difference in light gathering, but it does set them apart from the 8x42 models available.  A great example of an 8x43 birdwatching binocular is the Zen-Ray ZEN ED3 8x43 binocular, which is commonly accepted as one of the best performing models (and best value) available for birders under $500.
  
  
• 8x50 Binoculars: While not as common as the other options, these binoculars do exist.  They combine the ever-popular 8x magnification with a large 50mm objective, which collects more light than smaller models, and will produce brighter images in even the lowest of light conditions.  A tradeoff with 8x50 binoculars is usually field of view.  Due to the way they are designed, it can be more difficult to track birds.  
  
  The Vixen New Foresta 8x50 is a good choice for birders looking for the highest possible light gathering ability, while still keeping the 8x magnification.
   
• 10x32 and 10x42 Binoculars: The binoculars listed above are also commonly available with 10x magnification, which as mentioned before, are slightly more powerful, but present stability issues for some users.  If you have a steady hand and want a little more power, the 10x counterparts of the binoculars listed above are great options.
  
  
• 10x50, 12x50, and 15x50 Binoculars: As mentioned before, these binoculars have a larger size and more power, which doesn't really make them suitable for all-around birding.  They tend to be heavy and cause stability issues when using them for more than a glance.  However, they are a good option in situations where you have a tripod available, because these models can usually be mounted on a tripod for stable long term viewing.  For example, observing a nest of birds in the distance over the course of a few hours.